Systems and methods for patient control of stimulation systems

ABSTRACT

Provided is a portable controller and associated method that provides a patient or caregiver the ability to recharge and alter the parameters of an implanted medical device, while allowing the patient substantially unobstructed mobility. To enable mobility, the controller may be worn on a belt or clothing. The controller also allows the patient to turn device stimulation on and off, check battery status, and to vary stimulation parameters within ranges that may be predefined and programmed by a clinician. The controller communicates with the medical device to retrieve information and make parameter adjustments using wireless telemetry, and it can send and receive information from several feet away from the implanted medical device. Charging of a battery contained in the implanted medical device is achieved via an inductive radio frequency link using a charge coil placed in close proximity to the medical device.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/712,379, filed 28 Feb. 2007, now U.S. Pat. No. 9,480,846 to Strother,which is a continuation-in-part of co-pending U.S. patent applicationSer. No. 11/516,890, filed 7 Sep. 2006, and entitled “Implantable PulseGenerator Systems and Methods for Providing Functional and/orTherapeutic Stimulation of Muscles and/or Nerves and/or Central NervousSystem Tissue.” The entire content of each of these applications isincorporated herein by reference.

BACKGROUND

The invention relates generally to systems and methods for control ofelectronic devices. More specifically, the present invention relates tosystems and methods for the programming and recharging of medicaldevices, and especially neurostimulating devices, either by the patientreceiving treatment from the device or by a caregiver.

Medical devices are commonly used today to treat patients suffering fromvarious ailments, including by way of example, pain, incontinence,movement disorders such as epilepsy, Parkinson's disease, andspasticity. Additional stimulation therapies appear promising to treat avariety of other medical conditions, including physiological,psychological, and emotional conditions. As the number of stimulationtherapies increases, so do the demands placed on these medical devices.

Known stimulation devices, such as cardiac pacemakers, tachyarrhythmiacontrol devices, drug delivery devices, and nerve stimulators, providetreatment therapy to various portions of the body. While the presentinvention may be used with various medical devices, by way of exampleand illustration, an implantable pulse generator (IPG) device will bediscussed to illustrate the advantages of the invention. In the case ofproviding electrical stimulation to a patient, an IPG is implantedwithin the body. The IPG is coupled to one or more electrodes to deliverelectrical stimulation to select portions of the patient's body.Neuromuscular stimulation (the electrical excitation of nerves and/ormuscle to directly elicit the contraction of muscles), neuromodulationstimulation (the electrical excitation of nerves, often afferent nerves,to indirectly affect the stability or performance of a physiologicalsystem) and brain stimulation (the stimulation of cerebral or othercentral nervous system tissue) can provide functional and/or therapeuticoutcomes.

There exist both external and implantable devices for providingbeneficial results in diverse therapeutic and functional restorationsindications. The operation of these devices typically includes the useof an electrode placed either on the external surface of the skin, avaginal or anal electrode, or a surgically implanted electrode.Implantable medical devices may be programmable and/or rechargeable, andthe devices may log data, which are representative of the operatingcharacteristics over a length of time.

Implantable devices have provided an improvement in the portability ofneurological stimulation devices, but there remains the need forcontinued improvement in the control of such devices either by thepatient into whom a device is implanted or by a caregiver. Medicaldevices are often controlled using microprocessors with residentoperating system software. This operating system software may be furtherbroken down into subgroups including system software and applicationsoftware. The system software controls the operation of the medicaldevice while the application software interacts with the system softwareto instruct the system software on what actions to take to control themedical device based upon the actual application of the medical device.

As the diverse therapeutic and functional uses of stimulators increaseand become more complex, system software having a versatile interface isneeded to play an increasingly important role. This interface allows thesystem software to remain generally consistent based upon the particularmedical device, and allows the application software to vary greatlydepending upon the particular application. As long as the applicationsoftware is written so it can interact with the interface, and in turnthe system software, the particular medical device can be used in a widevariety of applications with only changes to application specificsoftware. This allows a platform device to be manufactured in large,more cost effective quantities, with application specific customizationoccurring at a later time.

While handheld programmers are generally known in the art, theprogrammers are generally controlled only by a treating physician orclinician. Therefore, to modify device settings, an office visit isnormally required. Such office visits are especially inefficient wherethe required adjustment of the medical device is such that the patientor caregiver could accomplish the adjustment with minimal training.Therefore, there exist many gaps in handheld controller devices andmethods for the controlling and recharging of medical devices,especially those of the implanted type, either by the patient receivingtreatment from the device or by a caregiver.

Furthermore, although it is generally known to use rechargeable powersupplies or batteries in implanted medical devices, methods heretoforeemployed to recharge the implanted devices most often required thepatient to remain relatively motionless or in a relaxed position. Sincethe recharging process for the devices can be lengthy, the limitationsin patient movement could hinder the patient's lifestyle, especially ifrecharging was required during the patient's waking hours. For example,a patient using a prior art method of recharge may be prevented fromrunning simple errands because of the virtual or physical tether toprior art recharging apparatus.

Therefore, the field of medical treatment by implantable medical deviceswould benefit from a portable apparatus that provides a patient orcaregiver the ability to recharge and alter the parameters of animplanted medical device, while at the same time allowing the patientsubstantially unobstructed mobility.

SUMMARY

The present invention comprises a portable apparatus and associatedmethod that provides a patient or caregiver the ability to recharge andalter the parameters of an implanted medical device, while at the sametime allowing the patient substantially unobstructed mobility.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a first embodiment of a handheldcontroller.

FIG. 2 is a perspective exploded view primarily showing the mainstructural components of the first embodiment of FIG. 1.

FIG. 3 is a front elevation view of the first embodiment of FIG. 1.

FIG. 4 is a top plan view of the first embodiment of FIG. 1.

FIG. 5 is a cross-section view of the first embodiment taken along line5-5 of FIG. 4.

FIG. 6 is a front elevation view of the first embodiment of FIG. 1,further including charging coil and power supply accessories.

FIG. 7 is a side elevation view of the charging coil of FIG. 6.

FIG. 8 is a perspective view of a second embodiment of a handheldcontroller.

FIG. 9 is a top plan view of a controller kit.

FIG. 10 is a first illustration of use of the embodiment of FIG. 1.

FIG. 11 is an illustration of use of an alternative embodiment of thehandheld controller.

FIG. 12 is a second illustration of use of the embodiment of FIG. 1.

FIG. 13 is a third illustration of use of the embodiment of FIG. 1.

FIG. 14 is an illustration of use of the embodiment of FIG. 8.

FIG. 15 is a diagrammatic illustration of an embodiment of software flowof software, utilized by a microcontroller in the handheld controller.

FIGS. 15A-E provide more specific embodiments of an implementation ofthe software flow embodiment of FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Although the disclosure hereof is detailed and exact to enable thoseskilled in the art to practice the invention, the physical embodimentsherein disclosed merely exemplify the invention which may be embodied inother specific structures. While the preferred embodiment has beendescribed, the details may be changed without departing from theinvention, which is defined by the claims.

Turning now to the Figures, FIG. 1 is a perspective view of a firstembodiment of a handheld patient stimulator controller 100. Thecontroller 100 comprises a base 102, a bezel 104, and a lens 106, all ofwhich, when assembled, form a protective shell 110, which generallycontains electronic circuitry. The base 102 is generally a hollow,bowl-shaped component having a bottom 102 a and a continuous wall 102 bextending therefrom. The bezel 104 has a first surface 104 a, which isdesirably adapted to be placed and secured in a mating relationship tothe base wall 102 b. The bezel 104 may be secured to the base 102 by wayof adhesive or even a locking physical structure, but more desirably byway of threaded fasteners. The bezel 104 also has a second surface 104b, which may be recessed, thereby providing a surface to which the lens106 may anchor. Both the base 102 and the bezel 104 are desirably moldedto any desirable shape using injection molding of a suitable materialsuch as Lustran® acrylonitrile-butadiene-styrene (ABS) 348 resin, or apolycarbonate ABS material that would allow thinner componentconstruction and enhanced shock absorption. The lens 106 has a firstsurface 106 a, which is adapted to rest against the bezel second surface104 b. To maintain proper positioning of the lens 106, the lens firstsurface 106 a may be provided with an adhesive. The lens 106 isdesirably formed by injection molding of a material that can offerdesired optical clarity. The shell 110 is desirably appropriately sizedto easily fit in a user's hand. For example, a desirable shell 110 maybe about the size of other small personal electronic devices that may beabout 7 centimeters long, about 4 centimeters wide, and about 1centimeter thick.

Disposed on or in the shell 110 are two interfaces; a user inputinterface 120 and a user output, or feedback, interface 130. The userinput interface 120 desirably comprises a plurality of buttons; a powerbutton 122, a mode select pad 124, and a parameter adjustment pad 126.The power button 122 is desirably a push button to power the controller100 on and off. The mode select pad 124 desirably provides two buttons;a mode up button 124 a and a mode down button 124 b. The adjustment pad126 also desirably provides two buttons; an increase button 126 a and adecrease button 126 b. Furthermore, a select button (not shown) may beincluded as a part of the user input interface 120, similar to the otherbuttons. The select button could provide a means of affirmativeindication by the user that a setting of the device 100 is acceptable.Desirably, all buttons of the user input interface 120 interface with atleast one electronic component contained in the controller 100. Thebuttons are desirably injection molded silicone rubber.

In addition to the user input interface 120, the controller 100comprises a user output interface 130. The depicted controller 100 isshown with a liquid crystal display (LCD) screen 131 as the user outputinterface 130. The function of the user output interface 130 is toprovide some visual feedback such as a status or operating mode of thecontroller. 100, a status of a medical device, or a preview ofprogramming parameters to be transferred to the medical device. Byutilizing the LCD screen 131, specific diagrammatic figures andparameter values may be displayed. Additional user output displaycomponents may include other visual indicators such as simplelight-emitting diodes (LEDs), or aural indicators such as piezo buzzersor variable audio tones.

FIG. 2 is a general exploded view of the controller 100 of FIG. 1,showing the basic assembly of the controller 100, and further showing aprinted circuit assembly (PCA) 150 on which electronic circuitrycontained in the shell 110 may be supported and interconnected. Insteadof using only a single PCA 150, a plurality of PCAs may be used.

Referring also to FIGS. 3 and 4, which simply show different views ofthe embodiment of FIG. 1, the controller 100 may be supplied with atleast one receptacle or port 140 for receiving plugs from externalaccessories or components. The one or more receptacles 140 areelectrically coupled to the appropriate electronic components. While aplurality of receptacles 140 could be provided, it is desirable to haveonly a single port 140 to allow the connection of only a singleaccessory at any given time. Where a single port 140 is meant to providean interface for a variety of accessories, the port 140 and theaccessory plugs may be keyed differently such that, by providingelectrical contact surfaces in different locations in connection withthe port 140, the controller 100 is able to distinguish betweenconnected accessories. The receptacle 140 is desirably covered with aprotective gasket 142, which prevents the receptacle 140 from beingcontaminated with dust or other particulates, and may protect thereceptacle 140 from exposure to moisture. The gasket 142 is desirablyinjection molded out of any suitable material such as Santoprene®thermoplastic elastomer, available from Advanced Elastomer Systems, LP.The gasket 142 is held in place desirably by the clamping force holdingthe base 102 and bezel 104 together.

FIG. 5 diagrammatically depicts electrical components arranged, in noparticular order, on the PCA 150, shown in FIG. 2, which is housed inthe shell 110. By way of electrical components, the controller 100desirably includes a power supply 152, a programmable microcontroller154, an accessory controller 156, a wireless telemetry module 158,electrical connectors 157, and user interface components 159, all inoperative electrical connection.

The power supply 152 may be a rechargeable battery 153 and associatedcharging and indication circuitry 155. The rechargeable battery 153 maybe recharged when connected to a power source, such as when thecontroller 100 is connected by a power adaptor 300 to a wall outlet, oris docked on a docking station (not shown). Addressing safety concerns,the controller 100 desirably may not be used to recharge an IPG 18 whilethe controller 100, itself, is being recharged through the power adaptor300. The charging and indication circuitry 155 provides to themicrocontroller 154 periodic updates of the status of the battery 153and charging thereof. The battery 153 is desirably secured in the shellso that it cannot be removed easily, so as to discourage accidentaldisposal by users.

The programmable microcontroller 154 provides the general intelligenceof the controller 100, and desirably includes a predetermined amount ofmemory to hold desirable software; however, the memory may also besupplied as a separate component. The microcontroller 154 generallycontrols the operation of the user output interface 130, the accessorycontroller 156 and the wireless telemetry module 158, all depending uponthe mode of operation as selected by the user input interface 120 orsome other source.

The accessory controller 156 is desirably a slave to the microcontroller154 and provides the requisite electronic control of an accessory, suchas a charging coil 200. The accessory controller 156 is activated by themicrocontroller 154 when the associated accessory is detected as beingcoupled to the controller 100 through the receptacle 140. A singleaccessory controller 156 may supply the requisite control of a pluralityof accessories, or, alternatively, a plurality of accessory controllers156 may be supplied.

The telemetry module 158 may incorporate a suitable wireless telemetrytransceiver chip set that can operate in the Medical ImplantCommunications Service (MICS) band (402 MHz to 405 MHz) or other veryhigh frequency (VHF) or ultra high frequency (UHF) low power, unlicensedbands. A wireless telemetry link established between the controller 100and an implanted medical device is especially useful in motor controlapplications where a user issues a command to an IPG to produce musclecontractions to achieve a functional goal (e.g., to stimulate ankleflexion to aid in the gait of an individual after a stroke). Thewireless telemetry is desirably non-inductive radio frequency telemetry.Therefore, communications between the controller 100 and the IPG 18desirably does not require a coil, or other component, taped or placedon the skin over the IPG 18, thereby enhancing user maneuverability andallowing communications desirably up to a distance of six feet betweenthe controller 100 and the IPG 18. A suitable transceiver chip that maybe used for half duplex wireless communications is the AMIS-52100,available from AMI Semiconductor, Pocatello, Id. This transceiver chipis designed specifically for applications using the MICS band and theMICS European counter-part, the Ultra Low Power-Active Medical Implant(ULP-AMI) band.

The electrical connectors 157 on the PCA 150 may provide operativeelectrical interconnectivity between the PCA 150 and various electricalcomponents, such as the LCD 131, the receptacle 140, other PCAs, or evena standardized test setup, such as a Joint Test Action Group (JTAG)interface.

User interface components 159 convert user input to electrical signalsto be used by the controller 100 and further convert electrical signalsinto indicators that are to be sensed by a user. As user interfacecomponents 160 to the user input interface 130, it is desirable toprovide a plurality of split electrical contacts 162 to indicate when auser has communicated through the user input interface 120. The contacts162 are electrically coupled to the microcontroller 154 to indicate suchuser activity. An electrically conductive surface is provided on abottom side of the plurality of buttons on the user input interface 120,so as to connect both sides of the split contacts 162 when a button isdepressed. Furthermore, the user interface components 160 furthercomprise the parts of the user output interface 130, such as the LCD131.

FIG. 6 shows the controller 100 with external accessories, which mayinclude a charge coil 200 and a power adaptor 300. The charge coil 200desirably includes a predetermined construction comprising a housing202, a coil cable 204, and a winding (not shown). The housing 202 ispreferably formed to a desirable size out of a thermoplastic elastomer,such as Santoprene®. Such material aids in avoiding skin irritation thatmay arise as a result of long term exposure of a patient's skin to othermaterials. The winding can be of various construction but is desirably150 to 250 turns, and more desirably 200 turns, of six electricallyparallel strands of #36 enameled magnetic wire, or the like.Additionally, the charging coil outside diameter may be in a range ofabout 40 millimeters to about 70 millimeters, and desirably about 65millimeters, although the diameter may vary. The thickness of thecharging coil 104, as measured perpendicular to its mounting plane, isdesirably significantly less than its diameter, e.g., about threemillimeters to about eleven millimeters, so as to allow the coil 200 tobe embedded or laminated in the housing 202 to facilitate placement onor near the skin. Such a construction allows for efficient powertransfer and allows the charging coil 200 to maintain a safe operatingtemperature. As seen in FIG. 7, the coil 200 may be provided with anadhesive backing strip 208 to be removably coupled to a patient's skin.The strip 208 may be formed of closed-cell polyethylene foam, whichwould prevent overheating of the patient's skin adjacent the coil 200.The strip 208 has a skin-side adhesive surface, which is desirablyprotected by a release liner 210. The release liner 210 preventscontamination of the adhesive strip 208 prior to application on theskin. Returning to FIG. 6, the coil cable 204 comprises insulatedelectrical conductors providing at least two conductive paths,operatively coupled to the coil winding at one end and to an electricalplug 206 at the other end. Therefore, one electrical path provideselectrical current to the coil 200 while the other path provides areturn current to the controller 100. The electrical plug 206 serves asthe electrical connection point between the controller receptacle 140and the coil 200.

The power adaptor 300 provides the ability to recharge the controllerbattery 153. It comprises a power plug 302, converter 303, and a powercord 304. The power plug 302 is a conventional power plug adapted tocooperate with any standard wall outlet socket. The converter 303receives alternating current power from the standard wall outlet socket,through the plug 302, and presents the appropriate voltage required bythe battery charging circuitry 155 in the controller 100. Theappropriate voltage is presented through the power cord 304, whichincludes a power connector 306, mateable with the controller receptacle140. Alternating current power cords are generally known in the art, andmany variations are available.

A second controller embodiment 400 is shown in FIG. 8. Like the firstembodiment 100, this controller 400 has a user input interface 420 and auser output, or feedback, interface 430. The user input interface 420comprises five buttons and a power switch 422. The power switch 422 ofthis embodiment 400 is desirably a single pole single throw slide switch422 recessed below the outer surface of the controller shell 410. Oncethe controller 400 is powered on, manipulation of the electronics isaccomplished through the five buttons on its face. The buttons aredivided into two pairs surrounding a center button 428. One pair ofbuttons defines a mode pair 432,434 and the second pair of buttonsdefines an adjustment pair 442,444. The center button 428 is desirably ageneral purpose “OK” or “Select” button. All buttons and switches of theuser input interface 420, are operationally coupled to at least some ofthe electronics contained in the controller 400.

The user output interface 430 is provided desirably in the form of aplurality of light emitting diodes (LEDs) 431-435. The LEDs havedifferent display functionality depending upon the incident operatingstate of the electronic components within the controller 400. Similar tothe first embodiment 100, the second embodiment 400 contains variouselectronic components (not shown). The second embodiment 400 desirablyincludes a non-rechargeable battery as its power supply and does notinclude an accessory controller. Therefore, the primary function of areduced size controller, such as the second embodiment 400, is theadjustment of stimulation parameters and monitoring of IPG status ratherthan recharging the IPG battery.

It is to be appreciated that the controller 100 may take on anyconvenient shape, such as a ring on a finger, a watch on a wrist, or anattachment to a belt, for example. It may also be desirable to separatethe functions of the controller 100 into a charger and a patientcontroller.

FIG. 9 depicts a controller kit 500 that may be provided in a packaging510 and including a controller 100, a charging coil 200, a power adaptor300, a second controller 400, a set of user instructions 520, a carryingcase 530, record media 540, and a remote device 600. The remote device600 may be a simple magnet that enables transcutaneous activation anddeactivation of an IPG 18 including magnetic controls, such as a reedswitch. The record media 540 may be paper or self-adhesive labels to beused by a patient or physician in conjunction with record keeping. Thepackaging 520 can be made from any method now known in the art such asplastic molding. The kit 500 may also be provided without the remotedevice 600, the second controller 400, the instructions 520, thecarrying case 530 or the record media 540.

Turning to FIGS. 9-13, methods of operation of the described controllerembodiments are explained herein. While the controller 100 may be usedwith a variety of devices, the working example herein will concern usein conjunction with an implantable pulse generator (IPG) 18. The IPG 18desirably incorporates a rechargeable battery that can be rechargedtranscutaneously and a non-inductive radio frequency (RF) wirelesstelemetry system to enable transcutaneous communication. With the use ofthe controller 100, a patient may control certain predefined parametersof the implantable pulse generator within a predefined limited range.The parameters may include the operating modes/states,increasing/decreasing or optimizing stimulus patterns, or providing openor closed loop feedback from an external sensor or control source.Wireless telemetry also desirably allows the user to interrogate theimplantable pulse generator 18 as to the status of its internal battery.The full ranges within which these parameters may be adjusted by theuser are desirably controlled, adjusted, and limited by a clinician, sothe user may not be allowed the full range of possible adjustments. Thatis, while a given IPG parameter may be adjustable by a clinician over anumber of settings, it is desirable that a patient have access to modifythe parameters over only a limited range, less than the number ofsettings than a clinician has access to. Therefore, a clinician maydevelop a desirable treatment regimen for a given patient's conditionand program the limited parameter range according to the treatmentregimen.

The rechargeable battery of the IPG 18 may be recharged by theapplication of a transcutaneous low frequency RF magnetic field appliedby a charging coil 200 mounted on a patient's skin or clothing andplaced over or near the IPG 18. The transcutaneous RF magnetic field mayhave a frequency range of about 30 Khz to about 300 Khz. To begincharging, the charging coil 200 is placed proximate the IPG 18 andconnected by the coil cable 204 to the controller 100, and electricallycoupled to the accessory controller 156 through the controllerreceptacle 140. The coil 200 may be held in place manually, but it isdesirable that the coil 200 be removably fastened to the skin by way ofthe adhesive backing strip (208 in FIG. 7), or inserted into a pouch(not shown) having an adhesive backing strip, the pouch being removablycoupled to the skin. Alternatively, the pouch (not shown) could becoupled to a belt or other supporting structure, which is then worn bythe user so as to properly position the coil 200.

FIG. 11 portrays an alternative application, in which it is anticipatedthat a controller 100 may include an internal charging coil 200. A user1 would then support or wear the controller 100, which includes theinternal charging coil 200, over the IPG 18 to recharge the IPG 18battery.

The controller 100 and the IPG 18, as shown in FIGS. 9 and 10 may alsouse wireless telemetry to provide a “smart charge” feature to indicatethat charging is occurring and to make corrections to allow for optimalrecharging and protect against overcharging. During a battery rechargeperiod, the smart charge causes the controller 100 to issue commands tothe IPG 18 at predetermined intervals, e.g., thirty seconds, to instructthe IPG 18 to confirm that the generated RF magnetic field is beingreceived and is adequate for recharging the rechargeable battery. If thecontroller 100 does not receive a response from the IPG 18 to confirmthat the generated RF magnetic field is being received, the controller100 may stop generating the RF magnetic field.

During the battery recharge period, the IPG 18 may transmit statusinformation, such as an indication of the battery charge status and anindication of the magnitude of power recovered by the receive coil 200,back to the controller 100.

Based on the magnitude of the power recovered, the smart charge allowsthe controller 100 to automatically adjust up or down the magnitude ofthe magnetic field and/or to instruct the user to reposition thecharging coil 200 based on the status information to allow optimalrecharging of the battery of the IPG 18 while minimizing unnecessarypower consumption by the controller 100 and power dissipation in the IPG18 (through circuit losses and/or through absorption by the implantablepulse generator case 20 and other components). The magnitude of the RFmagnetic field 100 may be automatically adjusted up to about 300 percentor more of the initial magnitude of the RF magnetic field and adjusteddown until the controller 100 stops generating the RF magnetic field.Adjustment of the RF magnetic field 100 may also result from sensing adesirable temperature on the skin side of the charging coil 200. Thatis, the magnitude may be increased or decreased if a sensed temperatureis low enough or too high, respectively. Temperature sensing may beachieved by any general way known in the art, such as a thermistor orthermocouple.

The instructions to the user to reposition the charging coil 200 may bea visual instruction, such as a bar graph on the controller 100, or adisplay on the controller 100 showing relative positions of the chargingcoil 200 and the IPG 18, or an audio instruction, such as a varying toneto indicate relative position, or a combination of instructions.

In addition to a rechargeable battery, the IPG 18 may incorporatewireless telemetry for a variety of functions, such as receipt andtransmission of stimulus parameters and settings, receiving requests forand transmitting battery and operating status, allowing user control ofthe implantable pulse generator 18, and for assisting in the control ofthe RF magnetic field generated by the controller 100. To enablereliable wireless communications, each IPG may have a unique signaturethat limits communication to only certain dedicated controllers. Thissignature could be a serial number that is stored in the IPG innon-volatile electronic memory or by other means. While an interfacedevice or controller used by a clinician or physician may be configuredfor use with many patients and many IPGs by configuring the clinicalprogrammer with various desired serial numbers, such broad functionalityis not generally desirable for patients or caregivers.

The controller 100 is desirably the master of all wirelesscommunications between it and an IPG 18. Therefore, to begin a wirelesscommunication, the controller 100 generates and sends a wirelesstelemetry communication to an IPG 18, the communication including theIPG's unique serial number and data elements that indicate thecommunication is a command from an external controller 100. Only the IPG18 having the unique serial number responds to the communication fromthe controller 100. The communication response includes elements thatindicate the communication is a response to a command from an externalcontroller 100, and that the communication is not a command from adifferent external controller.

Communications protocols include appropriate received message integritytesting and message acknowledgment handshaking to assure the necessaryaccuracy and completeness of every message. Some operations (such asreprogramming or changing stimulus parameters) require rigorous messageaccuracy testing and acknowledgement. Other operations, such as a singleuser command value in a string of many consecutive values, might requireless rigorous checking and no acknowledgement or a more loosely coupledacknowledgement. Integrity testing may be accomplished through the useof parity bits in the communication messages or even the use of a cyclicredundancy check (CRC) algorithm. Implementation of parity and CRCalgorithms are generally known in the communications art.

The timing with which an IPG enables its transceiver to search for RFtelemetry from an external controller may be precisely controlled (usinga time base established by a quartz crystal) at a relatively low rate,e.g., the IPG may look for commands from the external controller forabout two milliseconds at a rate of two (2) Hz or less. This equates toa monitoring interval of about ½ second or less. It is to be appreciatedthat an IPG's enabled transceiver rate and the monitoring rate may varyfaster or slower depending on the application. This precise timingallows the external controller to synchronize its next command with thetime that the IPG will be listening for commands. This, in turn, allowscommands issued within a short time (seconds to minutes) of the lastcommand to be captured and acted upon without having to ‘broadcast’ anidle or pause signal for a full received monitoring interval beforeactually issuing the command in order to know that the IPG will haveenabled its receiver and be ready to receive the command. Similarly, thecommunications sequence may be configured to have the externalcontroller issue commands in synchronization with the IPG listening forcommands. Similarly, the command set implemented may be selected tominimize the number of messages necessary and the length of each messageconsistent with the appropriate level of error detection and messageintegrity monitoring. It is to be appreciated that the monitoring rateand level of message integrity monitoring may vary faster or slowerdepending on the application, and may vary over time within a givenapplication.

The wireless telemetry communications may also be used in conjunctionwith the IPG battery charging function. It is especially useful in caseswhere two implant charger controllers 100 could be erroneously swapped,or where two or more IPGs 18 may be within wireless telemetry range ofeach other. For example, when two users live in the same home, a firstIPG 18 could communicate with its controller 100 even when the chargingcoil 200 is erroneously positioned over another IPG 18. The controller100 is configured to communicate and charge a specifically identifiedIPG, or a target IPG, which is identified by the unique signature orserial number. If the target IPG is wirelessly communicating with acontroller 100 that is erroneously positioned, the target IPGcommunicates with the controller 100 to increase the magnitude of the RFmagnetic field. This communication may continue until the magnitude ofthe RF magnetic field is at its maximum.

In order to stop a controller 100 from attempting to charge theincorrect IPG 18, the controller 100 may periodically decrease themagnitude of the RF magnetic field and then wirelessly communicate withthe target IPG 18 to determine whether the target IPG 18 sensed thedecrease in the magnitude. If the charging coil 200 is erroneouslypositioned over an IPG other than the target IPG 18, the target IPG 18will not sense the decrease and will indicate to the controller 100 thatit did not sense the decrease. The controller 100 will then restore theoriginal RF magnetic field strength and retry the reduced RF magneticfield test. Multiple failures of the test may cause the controller 100to suspend charging and notify the user 1 of the error. Similarly,should the IPG 18 not recover usable power from the RF magnetic fieldafter a few minutes, the controller 100 will suspend charging and notifythe user 1 of the error.

Operation of the system can perhaps best be described with a workingexample explaining different operating modes of the controller 100incorporating an LCD screen 131. Generally, the controller 100 operatesso as to provide an interface between an IPG and a patient in which thedevice is implanted, or a caregiver thereof. The controller 100 providesthe ability for the patient to recharge the IPG, query the IPG regardingits present settings, to adjust the IPG settings, and to recharge thecontroller 100. As shown in the flowchart in FIG. 15, an embodiment ofthe controller 100 desirably has nine different operating modes: OFF,PROD_ID, IMP_STAT, REV_ADJ, LOC_COIL, IMP_CHG, CHG_DONE, CTRL_CHG, andSN_MOD. For reasons explained in more detail below, only the first eightmodes are desirably available to the patient or caregiver, the ninthmode being controlled by a supervising physician. It is to be understoodthat not all of the modes of operation are mutually exclusive and,therefore, some modes may be functional at overlapping times. FIGS.15A-E provide an exemplary software flow.

OFF: The controller 100 may enter the OFF mode from any other mode by amere passage of time, or the user may affirmatively enter the OFF modefrom any operating mode.

While the controller 100 is in the OFF mode, controller powerconsumption is minimal and the user output interface 130 is desirablydeactivated.

Optionally, however, a simple “heartbeat” or other nominal indicationmay be shown on the output interface 130 to represent some state of thecontroller.

From the OFF mode, the controller 100 may enter the PROD_ID mode or theIMP_STAT mode. To enter the PROD_ID mode, there are desirably twomethods of removing the controller 100 from the OFF mode. First, a usercould depress the power button 122. While depression of other buttons onthe controller 100 could possibly turn the device 100 on, to minimizeaccidental activation, it is desirable that only one button, the powerbutton 122, activate the device 100. Second, a user could supply powerto the controller 100 through a power adaptor 300. Therefore, if thecontroller 100 entered the OFF mode without error, when the controller100 wakes from the OFF mode, it, desirably enters the PROD_ID mode. If,on the other hand, the controller 100 was in the IMP_STAT mode and had afatal system error occur prior to entering the OFF mode, the controller100, upon leaving the OFF mode, desirably enters the IMP_STAT mode withan error indicator displayed, as shown in one embodiment in FIG. 15E.

PROD_ID: The controller 100 may enter the PROD_ID, or productidentification, mode from the OFF mode.

Upon entering the PROD_ID mode, a temporary indicator such as aninformational screen, or “splash screen,” may be displayed, includinginformation such as device information, manufacturer, software revision,date, time, etc. This screen or plurality of indicators remains activefor a predetermined amount of time before entering the next mode.

From the PROD_ID mode, the controller 100 may enter the following modes:IMP_STAT, LOC_COIL, or CTRL_CHG. The mode following the PROD_ID modedepends on whether an accessory is connected, and, if so, whichaccessory is connected. If no accessory is connected, the mode switchesfrom PROD_ID to IMP_STAT. If the power adaptor 300 is connected throughthe controller receptacle 140, the next mode is CTRL_CHG. Finally, ifthe charge coil 200 is connected through the controller receptacle 140,the next mode is LOC_COIL.

IMP_STAT: The controller 100 may enter the IMP_STAT, or implant status,mode from the following modes: OFF, PROD_ID, REV_ADJ, LOC_COIL, IMP_CHG,or CTRL_CHG. If the controller 100 entered the OFF state during an errorcondition, powering on the controller 100 preferably places it in theIMP_STAT mode with an indication of the error state. Assuming noaccessory is connected as the controller 100 is exiting the PROD_IDmode, the controller 100 enters the IMP_STAT mode. From the REV_ADJmode, IMP_STAT is entered by a mere passage of one of the following: apredetermined amount of time after REV_ADJ mode was entered; apredetermined amount of time after any parameter modifications are made;or, a predetermined amount of time after a predetermined combination ofthe mode buttons 124 a,124 b are depressed. From the LOC_COIL mode orfrom the IMP_CHG mode, the controller 100 may enter the IMP_STAT modewhere a charge coil 200 is disconnected and fails to be reconnectedwithin a predetermined amount of time. From the CTRL_CHG mode, thecontroller 100 enters the IMP_STAT mode if the power adaptor 300 isdisconnected from the controller 100. The predetermined amounts of timemay be anything greater than zero seconds, but is desirably between 3and 30 seconds.

The IMP_STAT mode may be a desirable base operating mode on top of whichother modes may run. Upon entering the IMP_STAT mode, information isdisplayed to the user. If the cause of entering this mode is adisconnected charge coil 200, it is desirable to display an indicationof the charge coil 200 disconnect that has occurred. Furthermore,through the user output interface 130, it is desirable to convey threepieces of information. One item is the battery charge status of thecontroller 100. The other two items depend on whether successfulwireless communications can be established with the IPG 18. Ifcommunications are not established, a message to that effect isdesirably displayed. If communications can be established, the batterycharge status of the IPG 18 is displayed, along with a present parametersetting, such as a stimulus intensity level. Rather than the threelisted pieces of information, or in addition to that information, otherstatus indicators or user commands could also be displayed through theuser output interface 130.

From the IMP_STAT mode, the controller may enter the following modes:OFF, REV_ADJ, LOC_COIL, and CTRL_CHG. The user may do nothing, or maydepress the power button 122, for a predetermined period of time, andthe controller 100 desirably proceeds to the OFF mode. The user maydepress a button on the mode select pad 124 to enter the REV_ADJ mode.To enter the LOC_COIL mode, the user may connect a charge coil 200 tothe controller receptacle 140. Finally, the user may connect a poweradaptor 300 to the controller receptacle 140 and to an active wallsocket to enter the CTRL_CHG mode.

REV_ADJ: The controller 100 may enter the REV_ADJ, or review and adjustsettings, mode from the following modes: IMP_STAT or IMP_CHG. If theuser is in either of these modes and depresses the mode select button124, the controller 100 will switch into the REV_ADJ mode.

In this mode, the user has the option to adjust various settings both ofthe controller 100 and of the IPG 18. While the REV_ADJ mode is active,the mode select button 124 allows the user to scroll between parameters.For example, the user may wish to alter the volume of an audio indicatorfrom the controller 100. The user simply navigates to the volumeparameter using the mode select button 124 and then changes the volumesetting by using the parameter adjustment button 126. Other parametersmay be adjusted, such as IPG stimulation intensity and IPG stimulationactivation. The stimulation intensity is generally only a vague,abstract number to the patient. That is, the patient's physician willdictate the various stimulation profiles available to the patientthrough the use of the controller 100 in combination with the IPG 18.The patient will only see, desirably, a numerical indicator of whichprofile is activated and may possibly reference a correlative list ofwhat those numerical indicators actually mean with regards to thetechnical settings of the IPG 18, such as pulse width, amplitude andfrequency of the stimulation. Therefore, as seen in FIG. 12, thephysician 2 may establish a “normal” or baseline stimulation level andthe patient 1 may be able to adjust from the baseline plus or minusthree steps, however those steps may be defined by the physician 2. Inthe REV_ADJ mode, after the user has selected the desired value for theadjusted parameter, the controller 100 will indicate to the user thatthe parameter has been selected and is being transmitted to the IPG 18.Such indication could be accomplished a variety of ways, such asspecific iconic or textual displays, or even a simple change in theappearance of the screen, such as a flashing screen. Upon communicationof the changed parameters to the IPG 18, or a predetermined amount oftime thereafter, the controller 100 exits the REV_ADJ mode and returnsto the IMP_STAT mode. The controller 100 may also exit the REV_ADJ modeafter a predetermined input from the user input interface 120. Anembodiment of the flow through the REV_ADJ mode can be seen in FIG. 15B.Furthermore, should communications between the controller 100 and theIPG 18 be lost, an error message may be communicated through the useroutput interface 130, as shown in FIG. 15D. The controller 100 may thenattempt to restore communications with the IPG 18.

From the REV_ADJ mode, the controller 100 may enter all of the modesfrom which the mode may have been entered: IMP_STAT or IMP_CHG. The modeto which the controller 100 proceeds depends on which mode it was inbefore the REV_ADJ mode was entered. It may return to the mode fromwhich it came by the mere passage of a predetermined period ofinactivity, by the depression of the power button 122.

LOC_COIL: The controller 100 may enter the LOC_COIL, or locate chargingcoil, mode from the following modes: PROD_ID, IMP_STAT or IMP_CHG. Fromthe PROD_ID mode, if a charging coil 200 is coupled to the controller100, it enters the LOC_COIL mode automatically. From the IMP_STAT mode,rather than plug in the power adaptor 300 to the receptacle, the usercould connect the charging coil 200 to the controller 100 causing it toenter the LOC_COIL mode. From the IMP_CHG mode, if the inductivecoupling between the charge coil 200 and the IPG 18 becomes ineffectivefor purposes of charging, the controller 100 may be forced into theLOC_COIL mode. An implementation of the LOC_COIL mode can be seen inFIG. 15C.

Once in the LOC_COIL mode, a visual indication is displayed and thecontroller 100 emits a locating tone. The screen 131 displays agraphical indication of the quality of the charging coil 200 placementproximate the IPG 18, and further includes an indicator, graphical ortextual, that appears when the quality of the charging coil 200placement is adequate to allow normal charging of the IPG battery.Desirably, depression of either the mode button 124 or the parameteradjustment button 126 has no effect on the controller 100 during thetime it is locating the proper placement of the coil 200. Whilemaneuvering the coil 200 to locate the IPG 18, and throughout charging,the user is informed as to the quality and status of the chargingprogress, desirably visually and aurally. The user should especially beinformed if the coil cable 204 becomes unplugged from the controller100. Once the locating tone and/or display indicate that the coil 200 isin proper charging position, the user can begin charging by pressing thepower button 122 to enter the IMP_CHG mode.

Two periods of inactivity will cause the controller 100 to at leastimply repositioning of the coil 200 and/or the controller 100 to enableproper charging. First, if no wireless telemetry is successful for apredetermined period, the controller 100 warns the user of the lack ofwireless communications with the IPG 18. Also, during coil location,periodic updates of coil location quality are calculated to provideadequate feedback to the user. However, if no wireless telemetry betweenthe controller 100 and IPG 18 has been successful between apredetermined number of charge coil updates, the controller 100 will notindicate to the user that placement of the coil 200 is adequate fornormal charging.

From the LOC_COIL mode, the controller 100 may enter the followingmodes: OFF, IMP_STAT and IMP_CHG. Inactivity on the part of the user fora predetermined time, three minutes for example, desirably causes thecontroller 100 to enter the OFF mode. The IMP_STAT mode is entered whena charge coil 200 is disconnected and fails to be reconnected within apredetermined amount of time. The IMP_CHG mode is entered when the useris satisfied with the positioning of the charging coil 200 and atriggering event occurs. The triggering-event could be the depression ofthe power button 122 or the achievement of a predetermined chargingpower.

IMP_CHG: The controller may enter the IMP_CHG, or implant charging, modefrom the following modes: LOC_COIL or REV_ADJ. Entry into this mode, iscaused by the occurrence of a triggering event. The triggering event maybe a user-initiated event or an automatic reactive event. Theuser-initiated triggering event may be the depression of a button. Theautomatic reactive triggering event may be the mere passage of time, oreven a sensed charge coil placement position.

The IMP_CHG mode desirably runs on top of the IMP_STAT mode. Once in theIMP_CHG, an indication is displayed on the LCD 131. While in this mode,the accessory controller 156 is driving the connected charging coil 200.The user output interface 130 indicates to the user the fact thatcharging is taking place, and may also indicate the status of the IPGbattery charge. While in this mode, the user may also alter the settingsof the IPG 18.

From the IMP_CHG mode, the controller 100 may enter the following modesof operation: OFF, IMP_STAT, REV_ADJ, LOC_COIL, CHG_DONE, or CTRL_CHG.The user may affirmatively cancel the charging process, in which casethe controller 100 desirably enters the OFF mode or IMP_STAT mode.Depression of the mode select button 124 will cause the controller 100to enter the REV_ADJ mode and provide indication to the user. TheIMP_CHG mode completes when the IPG is fully charged or when the chargein the controller battery 153 is insufficient to continue adequatecharging. When the IMP_CHG is not interrupted and allowed to proceed tocompletion, the controller 100 enters the CHG_DONE mode.

CHG_DONE: The controller 100 may enter the CHG_DONE, or charge done,mode from the IMP_CHG mode. The CHG_DONE mode is entered upon theoccurrence of either a completely charged IPG 18 battery or upon thedepletion of the controller battery 153 to a point where further implantcharging would be ineffective.

Desirably, although continued IPG charging may not be allowed, thedepletion point would allow enough controller battery 153 charge toallow basic operation of the controller 100.

Status is communicated to the user through the user output interface130. Desirably, no wireless communications occur between the controller100 and the IPG 18 in this mode.

From the CHG_DONE mode, the controller 100 may proceed to the followingmodes: OFF or IMP_STAT. To place the controller 100 in the OFF mode fromthe CHG_DONE mode, the power button 122 is depressed for a predeterminedperiod of time, or the controller could enter the OFF mode after apredetermined period of inactivity. Alternatively, if the charge coil isremoved from the controller 100, it enters the IMP_STAT mode.

CTRL_CHG: The controller 100 may enter the CTRL_CHG mode from thefollowing modes: PROD_ID, IMP_STAT or IMP_CHG. Entering from eitherPROD_ID or IMP_STAT mode occurs if power is supplied to the controller100 by a connected power adaptor 300. The CTRL_CHG mode is entered fromthe IMP_CHG mode if the power adaptor 300 is coupled to the controller100 within a predetermined amount of time from a disconnection of thecharge coil 200. In this case, the unplugged coil 200 status may becommunication through the user output interface 130 prior to enteringthe CTRL_CHG mode.

While in the CTRL_CHG mode, an indicator is displayed to the userthrough the user output interface 130. Where the user output interface130 is an LCD 131, the indicator may be a separate screen, or simply anindicator displayed in combination with other screens. The indicationprovided may be that of the present controller battery 153 level and anindication that the battery is charging.

From the CTRL_CHG mode, the controller 100 may enter the followingmodes: OFF, IMP_STAT, or SN_MOD. The controller 100 enters the OFF modeif the power button 122 is depressed for a predetermined amount of time.The IMP_STAT mode is entered when the power adaptor 300 is disconnectedfrom the controller 100, or when the controller battery 153 has beencharged to a predetermined level. Finally, the controller 100 enters theSN_MOD mode when a certain combination of buttons is pressed.

SN_MOD: The controller 100 may enter the SN_MOD, or serial numbermodification, mode from the CTRL_CHG mode. The SN_MOD mode is entered bydepressing a certain combination of buttons on the face of thecontroller 100 within a predetermined time. This mode is desirably notavailable to the patient or caregiver and is supplied primarily formaintenance of the device or review of the device settings by asupervising physician.

While in the SN_MOD mode, the physician may modify the serial number ofthe IPG with which the controller 100 should be communicating. Thismodification is accomplished by using the user input interface 120 andthe user output interface 130.

From the SN_MOD mode, the controller 100 may enter either the OFF modeor the CTRL_CHG mode. To enter the OFF mode, the physician merelydepresses the power button 122 for a predetermined period of time. Ifthe power button 122 remains unpressed for a period of time, thecontroller 100 desirably returns to the CTRL_CHG mode from which it cameto enter the SN_MOD mode.

Lastly, turning to a method of operation of the second embodiment 400 ofthe handheld controller, depicted in a user's hand in FIG. 14. Withreference also to FIG. 8, a user turns the controller 400 on with thepower switch 422 to communicate with an IPG 18. The user has the abilityto switch modes using the mode up button 424 a and the mode down button424 b. Desirable modes are (1) query present setting of IPG 18, (2)change stimulation setting of the IPG 18, (3) query battery level of theIPG 18, and (4) query battery level of the controller 400. When thecontroller 400 is activated by the power switch 422, the default mode ismode 1. The current mode is reflected by a predetermined patterned flashor constant light of the first LED 431. To query the present setting ofthe IPG 18, that is, to determine the present operating conditions ofthe IPG 18, the user presses the center button 428. The user feedbackinterface 430 then displays the result of the query. The LEDcorresponding to the current IPG setting will flash a predeterminednumber of times. The user output interface 430 will then display themode it is in by maintaining an LED 431 lit. To switch modes, the user 1can scroll through the modes using the mode up button 424 a or mode downbutton 424 b. In mode 2, the user 1 can alter the stimulation profilewith the profile up button 426 a or profile down button 426 b. When mode2 is entered, the second LED 432 flashes a predetermined number times,and then the LED corresponding to the current IPG setting illuminatessteady for a predetermined amount of time. While the present setting LEDremains illuminated, the user 1 may propose a new IPG setting by usingthe profile up button 426 a or profile down button 426 b. The proposedsetting LED flashes. For example, if the IPG 18 is currently set tostimulation profile 3, the third LED 433 will remain lit. If the user 1hits the profile up button 426 a, the fourth LED 434 will flash and the3rd will remain lit. If, instead, the user 1 hits the profile downbutton 426 b, the second LED 432 will flash and the third 433 willremain lit. If the user 1 wishes to maintain the current setting, theuser 1 may hit the mode down button 424 b, which serves as a “Back”function. If the user 1 wishes to continue to the new setting, indicatedby the flashing LED, the user can hit the center button 428, whichserves as an “OK” function.

Thus, when the IPG battery power is queried, the LEDs would illuminatefrom left to right indicating percentage of battery life remaining.Thus, to indicate 80% IPG battery life, the four leftmost LEDs wouldilluminate. To indicate 40% IPG battery life, the two leftmost LEDswould illuminate. The LEDs would switch off at the earlier of apredetermined time or the turning off of the power switch.

FIG. 13 contemplates control of the handheld controller 100 by a remotecomputer 700 over an operative connection 702. The operative connection702 may be a packet switched connection established over a local areanetwork connection, a wide area network connection, a wireless networkconnection, an internet connection. Alternatively, the operativeconnection 702 may be a more direct connection such as a serial RS-232cable or USB cable. Over the operative connection 702, a supervisingphysician or other person with access may reprogram the handheldcontroller 100 or even query and modify parameters of an implantedmedical device 18.

The foregoing is considered as illustrative only of the principles ofthe invention. Furthermore, since numerous modifications and changeswill readily occur to those skilled in the art, it is not desired tolimit the invention to the exact construction and operation shown anddescribed.

We claim:
 1. A method comprising: transmitting a radio frequencymagnetic field from a charging coil of a recharging module positionedproximate to an implanted medical device to transcutaneously recharge apower supply of the medical device, wherein the recharging module is atleast partially disposed in a shell of a medical device controller; andcommunicating, using a telemetry module at least partially disposed inthe shell, with the implanted medical device via non-inductive wirelesstelemetry to receive status information from the medical device whilethe recharging module recharges the power supply of the implantedmedical device, wherein the medical device controller at least one ofadjusts a magnitude of the radio frequency magnetic field or instructs auser to reposition the charging coil based on the status information,and wherein the charging coil is at least partially disposed outside ofthe shell.
 2. The method of claim 1, further comprising adjusting themagnitude of the radio frequency magnetic field based on the statusinformation.
 3. The method of claim 1, further comprising instructing,via the medical device controller, the user to reposition the chargingcoil based on the status information.
 4. The method of claim 1, furthercomprising indicating a proximity between the recharging module and theimplanted medical device to a user via the medical device controller. 5.The method of claim 1, further comprising: sensing a temperature of thecharging coil during the transmission of the radio frequency magneticfield from the charging coil; and adjusting the magnitude of the radiofrequency magnetic field based on the sensed temperature.
 6. The methodof claim 5, wherein sensing the temperature of the charging coilcomprises sensing a temperature of the charging coil on a skin side ofthe charging coil.
 7. The method of claim 5, wherein adjusting themagnitude of the radio frequency magnetic field based on the sensedtemperature comprises increasing the magnitude of the radio frequencymagnetic field based on the sensed temperature.
 8. The method of claim1, further comprising issuing, during the transmission of the radiofrequency magnetic field from the charging coil, a command from themedical device controller to the implanted medical device at apredetermined interval instructing the implanted medical device toconfirm that the radio frequency magnetic field from the charging coilis being received.
 9. The method of claim 8, further comprising stoppingthe transmission of the radio frequency magnetic field from the chargingcoil based on not receiving the confirmation from the implanted medicaldevice.
 10. The method of claim 1, wherein the received statusinformation includes an indication of a charge status of a battery ofthe power supply of the implanted medical device and a magnitude ofpower received by a charging coil of the implanted medical device. 11.The method of claim 1, wherein the medical device controller includes auser interface for interaction with at least one of the recharge moduleor the telemetry module, and wherein the user interface comprises a useroutput interface.
 12. The method of claim 11, wherein the user outputinterface comprises a display.
 13. The method of claim 11, wherein theuser output interface comprises at least one light-emitting diode. 14.The method of claim 1, wherein the medical device controller comprises auser interface for interaction with at least one of the recharge moduleor the telemetry module, and wherein the user interface comprises a userinput interface.
 15. The method of claim 14, wherein the user inputinterface comprises a plurality of buttons.
 16. The method of claim 15,wherein the user input interface comprises no more than five buttons.17. The method of claim 1, further comprising delivering electricalstimulation to a patient from the implanted medical device.